The airmen, recently returned from a six-month stint flying combat missions over Syria and Iraq, recounted how American aircraft relentlessly pounded Islamic State jihadists fighting the Kurds in Kobane.

The heavy bombing, not seen since the 2003 US invasion of Iraq, helped the Kurds hold and eventually recapture the northern border town last month, a symbolic blow to the extremists who appeared on the verge of seizing Kobane in October.

"When you went to Kobane, you could almost guarantee you were going to release a weapon that day," said Captain Todd Saksa, a B-1 weapons systems officer.

The 31-year-old Saksa had flown other missions in Afghanistan but what was different this time was "the sheer number of weapons dropped," he said by phone from Dyess Air Force Base in Texas.

B-1 pilot Major Brandon Miller, 38, has been deployed five times in warzones, but he had never before dropped as many bombs as during the battle for Kobane.

"I personally went Winchester three times," he said. Before that, he had never emptied his weapons bay.

In previous six-month tours over Afghanistan, it was typical for his squadron to unload 15 to 20 bombs.

But in their last deployment, the squadron dropped more than 2,000 bombs and hit more than 1,700 targets, he said.

The B-1B Lancer was built in the 1980s during the Cold War to fly low and fast into Soviet air space.

But the supersonic plane became a "workhorse" for the American-led air campaign in Kobane, delivering much of the firepower that took out IS fighters and vehicles, US Air Force officers said.

Unlike fighter jets, the bomber -- dubbed "the Bone" by air crews -- is able to linger for hours over a target thanks to a large fuel tank and can hold a much larger payload of weapons, with roughly two dozen bombs of different sizes.

- Eight hours over Kobane -

In a six-month period, the B-1 flew 18 percent of all strike flights against IS and accounted for 43 percent of the total tonnage of munitions dropped in Syria, Iraq and Afghanistan, officials said.

The airmen with the 9th Bomb Squadron had deployed to the Middle East in July preparing for missions over Afghanistan, where a small US force rarely if ever would call in a bombing raid.

But one night in August, a B-1 was ordered to hold on the runway. Instead of Afghanistan, the four-man crew was told they would be heading to northern Iraq to escort planes dropping supplies to encircled Yazidis on Mount Sinjar.

By October, the bombers were frequently flying to aid the embattled Kurds in Kobane, staying eight hours overhead -- with one mid-air refueling at the four-hour mark -- looking for IS fighters who were often in plain sight.

The targets were either spotted by the crews or relayed by Kurdish fighters, whose requests would be passed to America's air operations center in Qatar.

Without US forward air controllers near the front line, approval for a strike could take up to 45 minutes, officers said.

The IS fighters, unaccustomed to being hunted from the air, took a pummeling -- until they learned to conceal their movements.

The bombers were often joined by two or more F-15 or F-16 fighter jets, ensuring that "we had air power overhead almost 24 hours a day in Kobane," said Lieutenant Colonel Ed Sumangil, 40, commander of the squadron.

And unlike the past decade of US wars where insurgents often relied on roadside bombs and ambushes, there was a clear front line in Kobane, a conventional battle between two forces and no civilians nearby.

"There were good guys on one side and ISIL (IS) on the other side," Miller said.

The front line, or what the pilots call the "forward line of troops," shifted day to day, and sometimes hour to hour in favor of the Kurds.

- 'Rings of light' -

At night, the pilots could see see the outlines of the Turkish border near Kobane as it was "well lit," Miller said, while the Syrian side of the border was covered in darkness.

On the last flight of his tour in January, things looked different.

"Two of the strategic hills that are in Kobane, both had lights on around them, which was actually kind of shocking to see because it had been dark there the entire time," Miller recalled.

"And all of a sudden there were very well-defined rings of light around these mountains. The lights were starting to come back on in Kobane."